1. Field of the Invention
The present invention generally relates to a scanner, and more particularly to a portable scanner.
2. The Related Art
In order to use, storage and publish documents more efficiently and conveniently, ordinary documents written or printed on paper would be converted to digital data by virtue of optical scanners for the convenience of follow-up application. Referring to FIG. 1, one of the conventional optical scanners is a flatbed scanner 90. The flatbed scanner 90 includes a scanning plate 91 for bearing documents and a movable scanning device 92 movably mounted over the scanning plate 91. In use, the document is put on the scanning plate 91, then the movable scanning device 92 is driven to move along the document and scan the document. The flatbed scanner 90 can provide the high quality image, because the document is held still on the scanning plate 91 and the movable scanning device 92 can scan the document smoothly. However, the flatbed scanner 90 has too big size to be portable. Therefore, portable scanners came with the tide of fashion.
Referring to FIG. 2 and FIG. 3, the conventional portable scanners are generally sorted into two kinds of which one is designated as an auto-feed scanner 80 shown in FIG. 2 and the other is designated as a hand-held scanner 70 shown in FIG. 3. Referring to FIG. 2, the auto-feed scanner 80 can scan the document smoothly and automatically like the flatbed scanner 90. In order to make the auto-feed scanner 80 smaller, it includes an immovable scanning device (not shown) fastened in the auto-feed scanner 80 and a document feeder 81 for automatically transmitting documents through the immovable scanning device. Therefore, the auto-feed scanner 80 is easier to be carried and also able to provide the high quality image. However, the auto-feed scanner 80 fails to scan the document which is larger than the scanner in size.
Referring to FIG. 3, in order to make the hand-held scanner 70 smaller, an immovable scanning device (not shown) is fixed in the hand-held scanner 70. But the hand-held scanner 70 has no function of automatically transmitting the documents through the immovable scanning device. As a result, in use, the user has to manually swipe the hand-held scanner 70 through the document. So, the hand-held scanner 70 can scan documents in almost any size or any shape. However, the image quality provided by the hand-held scanner 70 is not as good as the auto-feed scanner 80 or the flatbed scanner 90. Because the foregoing scanning process is achieved by the manual operation, it is difficult to swipe the hand-held scanner 70 at a constant speed, besides, the hand-held scanner 70 is apt to diverge from the predetermined scanning path or be shaken in the process of being swiped. As a result, a twisted or deform image is often provided by the hand-held scanner 70.
In view of these disadvantages above, the conventional portable scanner needs to be improved.